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through 40 mm ball valves. An elbow pointing downwards directs the flow into the raceway. Unions fitted in line allow for replacement of parts and cleaning of pipes.

The front elevation of supply to the raceway is depicted in the technical drawing diagram – 2/Pg17. From the main seawater supply running on the ground along the periphery of the concrete pad, flow is directed upwards via a T-junction capped with clean-out valve for maintenance purposes. A 50 mm union is fitted in-line for ease of dismantling followed by a 50–40 mm bushing reducing the seawater supply line to 40 mm. The line runs in the middle of the raceway frame to the top of the channels; at this point, seawater is equally diverted to both raceway channels via a 40 mm T-junction.

4.1.2.2 Sieve layoutRefer to Technical Drawing – 3/Pg16B and 4/Pg16B. Each 25 mm drainage pipe connecting the raceway channel to centre drainage channel is fitted with a 25 mm coupling and pipe connected to each sieve. Sieves are 30 cm diameter, 10 cm high with a 1.06x0.72 mm (1.2 mm diagonal) mesh bonded to its base. This provides for a total of 12 spat holding sieves when the raceway is fully utilized.

The procedure for making sieves is similar to that described in Appendix 17. The mesh used to line the bottom is the same as that used for green collector bags with an aperture size of 1.2 mm on the diagonal. Fitting of the sieves to the raceway and outflow system differed from the indoor raceway system. A 25 mm hole is drilled onto the top of the sieve, through which a 25 mm pipe is tightly secured, extending on either side of the sieve wall by 50 mm. A 25 mm coupling is fitted into the 25 mm pipe in the interior of the sieve. The opening of the coupling is closed by a piece of 1.2 mm mesh to prevent any spat from flowing out. The overflow pipe is secured into the wall of the trough by tightening it into the drilled hole (see technical drawing photo – 4/Pg16B). Sieves are suspended off the bottom; and water flow is directed so as to move through the bottom mesh and out at the top of the sieve into the centre drainage channel, causing an upwelling movement.

Note: The system can readily be adapted for a downwelling flow by inputting water into the central channel and discharging the waste water through 40 mm diameter drainage pipes at the outflow end of each raceway compartment. In this case, the flow enters the sieve at the top and flows vertically downwards through the mesh of the sieves.

4.1.2.3 Outdoor raceway elevations and algal supplyRefer to Technical Drawings – page 17 and page 18). Colour codes for seawater are blue and purple for ambient supply and outflow; additionally, algal supply is coded in green.

The side elevation diagram (see technical drawing – 1/Pg17) depicts the plastic cylindrical tank used as an algal reservoir (56 cm diameter, 75 cm high tank; Volume of 150 l). In order to allow for supply or outflow of algae and seawater, three 20 mm holes are drilled into the wall of the tank. Two holes, on opposite sides of the tank, are close to the top and one is at the bottom. Position of the holes can be seen in the photos (see technical drawings – 1/Pg18 and 2/Pg18). The holes are sealed with an O-ring and fitted with a 20 mm female adapter to 20 mm male adapter to make a watertight connection.

There is a small demand for seawater supply to the algal tank on a daily basis for diluting of algal ration and cleaning of tank. For this purpose, the ambient seawater line coming from the pump house is first diverted to fill the algal tank (see technical drawings – 1/Pg17 and 1/Pg18). It is immediately reduced to 20 mm by a 50 mm to

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Technical drawing, Pg. 17Outdoor raceway and algal supply elevations

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Technical drawing, Pg. 18Outdoor raceway: Algal and seawater supply photographs

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20 mm adapter. A 20 mm union fitted in line allows for removal of tank and cleaning of pipes when necessary. Flow is regulated by a 20 mm ball valve; seawater passes through the tank wall, and is directed downward via a 20 mm elbow. Note: A bleed line (7 mm Tygon tubing) for the seawater supply, is put in as a precautionary measure, but was actually never needed; it is not recorded in these diagrams, but can be seen in the technical drawing photo – 1/Pg18).

For algal supply to the raceway channels, algal solution is pumped from the bottom of the 150 litres tank and runs through a 20 mm pipe parallel to the ground. Two 20 mm union are fitted in line close to the algal tank for daily cleaning of the tank. A 20 mm T-junction, capped on one end for cleaning, directs the flow to a quiet vertical pump Fittings for the pump are typical, as described in the technical drawing – page 15, and are supplied with the pump. Algal solution is passed through a 20 mm pipe alongside the raceway wall. Each end is capped by a cleaner valve, facilitating cleaning using a pipe brush. The algal line follows the contour of the raceway channels, running along the width of the channels. For each raceway channel an 8 mm male NPT fitting (hose barb) is threaded into an 8 mm hole. Algal feed is provided through Tygon tubing (7 mm) and regulated by a stopcock valve. Algae are thus continuously injected into the raceway channels at the point of seawater inflow. As pressure from the pump is high, and flow of algae restricted into raceway, an overflow valve is fitted following a T-junction (at the top of the algal tank) in the algal supply line; excess algae is thus passed through a 20 mm pipe through the tank wall for recycling. Any excess algae is mixed into the tank, as it is forced through a 20 mm perforated pipe running the length of the 150 litres tank, stopping 25 mm off the bottom.

The elevation view for the entire raceway also depicts the roof of the raceway and its wooden framework supporting the canopy, the stacked concrete blocks elevating the raceway to waist level, the concrete pad and seawater inflow and outflow. The framework supporting the canopy drawn is a sound engineering design and differs to that quickly constructed at the Bermuda hatchery (see technical drawing photo – 2/Pg16).

Technical drawings photos – 2/Pg18 and 3/Pg18 clearly illustrate the location of the algal supply line relative to the seawater supply line.

4.1.3 Circular tanksRefer to Technical Drawings – page 7, 19A and page 19B. The seawater and air supply lines for all tanks including the circular tanks described in this section are shown in a general ceiling plan in technical drawing – page 7. As a reminder, ambient seawater lines (coded blue) and heated seawater lines (coded red) run parallel to each other along the length of the container.

Refer to technical drawing – 1/page 7. Circular tanks are connected to both the heated seawater line and ambient seawater line via three connections. Ambient seawater, filtered to 1 µm, is diverted from the main line via a 40 mm T-junction; for the first connection, seawater is directed to the left, for the other two connections, seawater is directed to the right). The end of the 1 µm filtered seawater line is capped). All connections are similarly fitted, and details of one connection are shown in the technical drawing photo – 1/Pg19A. The connections are identical for both heated and seawater line. In-line of main supply pipes a 40 mm T diverts the flow of water downwards towards the circular tank. A 40 mm to 25 mm bushing reduces the circular tank line to 25 mm. The flow of seawater is regulated by a 25 mm one-way ball valve, glued to an elbow. This elbow allows for ambient seawater to flow into the circular tank. A 25 mm union is glued in line for cleaning and/or replacing of parts. After the union is a 25 mm T-junction directing the water flow to the circular tank and connecting this inflow

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Technical drawing, Pg. 19ACircular tanks: Plan and elevation